Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2004
Sammendrag
The process of model building in the environmental sciences and when dealing with ecosystems is discussed. Two types of modeling approaches need to be distinguished: An algorithmic one, which has been used traditionally in physics, meteorology, and other branches where biological degrees of freedom are either absent or neglectable; and an interactive one, which is a new framework in computer science and seems to be most suitable in cases where organisms (including humans) as agents in ecosystems are to be taken into account. The first modeling approach is exemplified by state models in dynamic systems theory and expresses the correspondence imposed by Natural Law between inferential entailment in a formal system and causal entailment in natural systems. Modeling is to be separated from simulation. Simulation is a less restrictive type of modeling in which the description of non-interactive behaviour is the purpose and no constraints on the correspondence to internal states are imposed. The second (new) modeling approach is exemplified by interactive simulation models. It is able to express the correspondence in behaviour imposed by engineering standards (or cultural norms in general) between documentation, training and application in interactive choice situations such as games or ecosystem management. It generalises the notion of simulation for interactive problems. In an idealised situation the strictest correspondence between behaviour in a natural and a virtual system is expressed as bisimulation. The principles for model building are shortly demonstrated with examples.
Forfattere
Petter Snilsberg Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
The forest stand growth simulator TRAGIC (tree response to acidification in groundwater in C) which has been developed to serve as a decision support system and a visualisation tool for scientists and forestry practitioners is introduced. TRAGIC places an emphasis upon visualisation techniques while at the same time providing detailed information on tree physiology and related parameters. The model is calibrated numerically to growth history data from two different European sites.Next, due to the importance of the visual component of the model, its ability to reproduce forest stand spatial structure is investigated, using an application of the theory of marked point processes. This analysis is applied to different experimental data sets for stands of different age, revealing information on planting schemes and the extent of significant spatial correlations.The spatial structure of the two model calibrations is then explored with the same methods. The point process analysis turns out to be a powerful diagnostic for model quality assessments, since spatial distribution is an indirect result of competition between trees for light.
Sammendrag
Målsetting med prosjektet har vært å 1) klarlegge vegetasjonssoners effekt på tilbakeholdelse av partikkelbundne pesticider ved overflateavrenning fra jordbruksarealer, 2) bestemme potensialet for nedbrytning av partikkelbundne pesticider i jordprøver fra vegetasjonssona og 3) validere modeller som beskriver effekten av vegetasjonssoner på avrenning av pesticider som bindes til partikulært materiale. Ugrasmiddelet glyfosat og soppmidlene fenpropimorf og propikonazol er brukt i prosjektet. Resultatene viser at gjennomsnittlig renseeffekt gjennom en 5 bred vegetasjonssone var høy; 51-62 % for partikler, 39-48 % for glyfosat, 34-71 % for fenpropimorf og 63-85 % for propikonazol. Glyfosat har sterk binding til jord, noe som kan forklare godt samsvar mellom renseeffekt for partikler og glyfosat/AMPA, mens fenpropimorf og propikonazol har moderat binding til jord. Forskjellen i Kd-verdi innenfor et begrenset område er imidlertid stor, og viser at stedsspesifikke data er nødvendig. Over 80 % av total overflateavrening oppsto i løpet av vinterhalvåret, mens vinternedbøren var 28 % av totalnedbøren. Det var ingen signifikant forskjell i renseeffekt (%) for noen av parametrene mellom sommer og vinter, men total renseeffekt (i g) var større om vinteren pga høyere avrenning. Dette er sannsynligvis pga løsrivelse av grovere aggregater om vinteren, som sedimenterer lettere i vegetasjonssona. Løst og lett tilgjengelig glyfosat blir raskt nedbrutt, mens sterkt bundet glyfosat som er lite tilgjengelig, blir sakte nedbrutt. Halveringstiden for alle stoffene er lang og bindingsgraden stor slik at spredningen vil være dominert av partikkelbundet materiale. Vegetasjonssoner kan derfor være en effektiv måte å redusere forurensning av elver og sjøer. Simulering med GLEAMS modellen overestimerer overflateavrenning av glyfosat og fenpropimorf, mens total avrenning av propikonazol ligger innenfor et akseptabelt nivå. Modellen er svært sensitiv for avrenning i perioder nær frysing og tining, særlig senhøstes. Simuleringene har vist at problemstillingen frysing/tining ikke er tilfredsstillende løst og det er derfor nødvendig å se nærmere på den nye versjonen GLEAMS 3.0.
Forfattere
N. Syversen Roar Linjordet Ole Martin Eklo Christian ThorstensenSammendrag
Det er ikke registrert sammendrag
Sammendrag
The notion of an ecological damage has so far neither been given a proper theoretical nor a pragmatic or operational foundation. Yet one of the most widespread motivations for the scientific study of ecosystems is a “protectional” one by which an improved scientific understanding is sought in order to be able to prevent future ecological damages. We review the possibilities of valuating changes in the environment, in health or in ecosystems as a damage. The conceptual separation of potential from actual behaviour/structure is a prerequisite to any of them. The critical point here is the formal and empirical basis for the knowledge about these potentials. We contrast the dynamic systems theory approach derived in physics with an interactive computing approach recently developed in computer science. The former requires to distinguish facts and values and leads to notorious difficulties when applied at the ecosystem level. The latter and novel approach opens the possibility for a consistent definition of a damage at the ecosystem level whenever a tradition of (sustainable) utilization of such systems is available. The documentation, actualisation and dissemination of the tacit (expert) knowledge can be improved by the use of interactive simulations in which a virtual standard can defined by the respective experts themselves.
Sammendrag
Feeding ecology of piscivorous brown trout was studied in the Pasvik watercourse, Norway and Russia. The watercourse is heavily regulated for hydroelectric purposes, and 5000 brown trout >25 cm are stocked annually to compensate the negative impacts of the impoundments. Stocked and wild trout had almost identical diets consisting mainly of vendace Coregonus albula and partly of whitefish Coregonus lavaretus. Vendace is a recent invader to the watercourse and totally dominated the brown trout diet in the upstream part, where vendace has become the dominant species in the pelagic habitat. In the downstream part where vendace were less prevalent, whitefish contributed to a larger component of the trout diet. No correlation between predator (brown trout) and prey (vendace) length was found in the upstream part, and only a weak positive correlation was found in the downstream part. The length of whitefish eaten by brown trout, in contrast, showed a positive correlation with predator length in both the upstream and downstream part. The prey selection of brown trout was, to a large extent, explained by the differences in density and size-structure of coregonids in the two sampling areas.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Svein Solberg Kjell Andreassen Nicholas Clarke Kjetil Tørseth Ole Einar Tveito Geir-Harald Strand Stein Michael TomterSammendrag
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Sammendrag
Det er ikke registrert sammendrag